WASHINGTON - A U.S. Air Force helicopter crashed in Afghanistan (news - web sites) Sunday, killing all six people on board, the U.S. military said.

The HH-60G Pave Hawk helicopter was on a medical evacuation mission when it crashed at about 11:20 a.m. EST, about 18 miles north of Ghazni, Afghanistan, U.S. Central Command said in a statement.

The helicopter was not shot down, the statement said.

The precise cause of the crash is under investigation.

U.S. Military officials in Washington and Afghanistan said The medical emergency and the helicopter flight was not in connection with Operation Valiant Strike, a mission involving members of the Army's 82nd Airborne Division in southeastern Afghanistan.

That mission, which began earlier this month, is meant to root out remnants of the al-Qaida and Taliban believed to be operating in the area.

The last helicopter crash in Afghanistan was Jan. 30, when an Army Black Hawk helicopter — the Army's version of the Pave Hawk — on a training mission crashed near the Bagram air base, killing four.